1880.] Influence of Electric Light upon Vegetation. 



293 



helices, provided the ends of the helix wires are connected together 

 either singly in two separate circuits, or together in one continuous 

 circuit. Every up or down movement of either of the helices produces 

 currents in the wires either for or against magnetization, which 

 currents apparently so disturb the molecules of the iron that the 

 fixity of their original magnetic direction is lost. 



In like manner as the movements of the armature, or the increased 

 or diminished tension of the iron, produce currents of electricity in 

 the helix wires surrounding the magnets : so the movements of the 

 helices produce currents of electricity which may either magnetize or 

 demagnetize the iron. With the 58 lb. magnet in closed circuit, the 

 two ends of one of the helices being connected to the galvanometer, 

 and the two ends of the other helix being connected with each other, 

 the latter helix is moved towards the armature, a current is produced 

 in the galvanometer helix which shows a fall of magnetization. On 

 moving the same helix away from the armature, a current is produced 

 in the direction of magnetization. 



In another experiment 30 yards of No. 16 covered copper wire, 

 with its ends connected together, and so coiled that it could be moved 

 freely from pole to pole over the armature, was placed on one limb of 

 the 58 lb. magnet and the closed circuit established. Both helices 

 were then brought into continuous circuit through the galvanometer. 



On movement of the coil of wire from south limb to the north limb 

 of the magnet, a current was produced showing an increase of mag- 

 netization. On moving the coil in the opposite direction, i.e., over the 

 north limb pole, and on to the south one, the current is reversed, and 

 is in a direction which would cause demagnetization. 



It appears, therefore, that any interference with the lines of force 

 about a magnetic circuit, means an interference with the magnetic 

 circuit itself, and points to the possibility of building up magnetic force 

 of magnets by the mere movement of wires in these lines of force, 

 though the coils moved need not of necessity be connected with the 

 helices surrounding the magnets. 



VII. " Some further Observations on the Influence of Electric 

 Light upon Vegetation." By C. William Siemens, D.C.L., 

 LL.D., F.R.S. Keceived March 18, 1880. 



When upon the 4th of March, I presented to the Royal Society a 

 paper on the above-named subject, I was able to show by the result of 

 experiment the effect of radiation from the electric arc in promoting 

 the formation of chlorophyll within the leaf-cell of plants, and in 

 favouring vigorous and continuous growth. 



I ventured to express an opinion that the ripening of fruit would 



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